"junit.framework.AssertionFailedError: null" in Grails Unit Test - unit-testing

Question

I'm new to grails and am trying to get some tests running. I have two classes:
class Category {
String name;
}
class Animal {
Category category1
Category category2
boolean addCategory(Category category) {
if (!category1) {
category1 = category
return true
}
else if (!category2) {
category2 = category
return true
}
return false
}
boolean hasCategory(Category category) {
return category1 == category || category2 == category
}
}
Now I wrote a test that should check that adding more than two categories fails and that the third category would not be part of the categories:
class AnimalTests extends GrailsUnitTestCase {
protected void setUp() {
super.setUp()
}
protected void tearDown() {
super.tearDown()
}
void testMaximumCategories() {
Category category1 = new Category(name: "Category 1")
Category category2 = new Category(name: "Category 2")
Category category3 = new Category(name: "Category 3")
Animal animal = new Animal(title: "Animal")
assertTrue(animal.addCategory(category1))
assertTrue(animal.addCategory(category2))
assertFalse(animal.addCategory(category3))
assertTrue(animal.hasCategory(category1))
assertTrue(animal.hasCategory(category2))
assertFalse(animal.hasCategory(category3))
}
}
This test always fails in the last line and the stacktrace is the following
null
junit.framework.AssertionFailedError: null
at junit.framework.Assert.fail(Assert.java:47)
at junit.framework.Assert.assertTrue(Assert.java:20)
at junit.framework.Assert.assertFalse(Assert.java:34)
at junit.framework.Assert.assertFalse(Assert.java:41)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeStaticMethod(MetaClassImpl.java:1323)
at groovy.lang.ExpandoMetaClass.invokeStaticMethod(ExpandoMetaClass.java:1082)
at org.codehaus.groovy.runtime.callsite.StaticMetaClassSite.callStatic(StaticMetaClassSite.java:62)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallStatic(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:165)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:173)
at animal.AnimalTests.testMaximumCategories(AnimalTests.groovy:23)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
...
What am I doing wrong?

Answer 1

When I copy/pasted your code it failed since there's no title property in the Animal class. This might be an artifact of converting real code to demo code, but it could cause some compiler weirdness. Try running grails clean to force a full compile. Once I added a title field it worked fine.